Uneven Turning--Problem and Solution

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EricRN

Member
Joined
May 16, 2019
Messages
376
Hi all,

I'd been really frustrated lately because I'd not been getting an even turn on my pens. The lathe would vibrate ever so slightly, and the pens would not be even by a very slight amount--less than a millimeter but plenty big enough (to the discerning eye) to cause the fittings to be offcenter when I mounted them to the blank for final assembly. The classic problem here, is that the mandrel got bent. So I tried a different mandrel. Same problem--both of them must be bent. But I kept rolling them on my workbench looking for slight amounts of light and any lack in uniformity, to no avail. And I use a mandrel saver so I was kind of surprised that they could be bent at all. I was really stumped.

So I said, I"m going to turn between centers. I'll get rid of the mandrel entirely. I had some convertible bushings. I don't normally like TBC because I like to turn the body and cap at the same time, but these were for a one-piece twist pen so I figured why not. Same problem. An off center turning. Now I was really stumped. I had no idea what was going on or what could be causing the problem. I was worried that I'd somehow messed up the headstock on my lathe and got that spinning off axis or some other such problem.

So I removed the pen, pushed the tailstock up to the dead center I'd had in the headstock for my TBC bushings. And I rotated slowly, by hand. The dead center moved around the tailstock point in a circle of about 1 mm radius. I was really worried and really concerned, thinking this would be an expensive fix.

I took the dead center out and stared at the machine, contemplating the least expensive way to figure out what was going on, and then I saw it. I small chip of wood from one of my previous turnings had made its way into the headstock and gotten smooshed against the interior of the headstock where you put the morse taper. It was small enough to push anything I put in there into a slight angle. I cleaned it out, put the center back in and tested it. Good as new. And, thankfully, I was able to selectively sand down the side of the body that was too long relative to the other and get a perfectly fitted pen.

Moral of the story: Keep your headstock clean.
 
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leehljp

Member Liaison
Joined
Feb 6, 2005
Messages
7,721
Location
Tunica, MS,
Eric,

So many times the solutions is just stopping, trying, thinking a minute and looking. The world has seemed to have lost the observation deduction problem solving kind of thinking. I am glad you posted this! Maybe it will help some others to think through the problems for solutions! The world needs more people like this! 👍
 

Mortalis

Member
Joined
Aug 19, 2013
Messages
403
Location
Rochester, Mass
Every time I change from my blank drilling chuck to my center turning center I stick my little finger in the taper of the tail stick and the headstock to feel for any chips. I them look into each taper and then use my compressed air to blow anything that may be left in the taper out. I then make sure that when I insert my center and drill chuck that they be easily sit in the tapers. It doesn't take much to ensure the tapers lock.
 

ed4copies

Local Chapter Manager
Joined
Mar 25, 2005
Messages
24,038
Location
Racine, WI, USA.
I am changing often, as I do more "steps" on the lathe. I have made a major purchase at my local
"Everything for a buck" store--a bottle brush. Run the lathe headstock at very low RPM and insert
the bottle brush--works neat!! Then insert the dead center (Or whatever you will use next) and check to be
sure it is running true.
 

KenB259

Member
Joined
Dec 24, 2017
Messages
1,215
Location
Michigan
I am changing often, as I do more "steps" on the lathe. I have made a major purchase at my local
"Everything for a buck" store--a bottle brush. Run the lathe headstock at very low RPM and insert
the bottle brush--works neat!! Then insert the dead center (Or whatever you will use next) and check to be
sure it is running true.

I also use a bottle brush, I think I got a 3 pack for just a couple dollars.



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bsshog40

Member
Joined
Oct 2, 2018
Messages
1,823
Location
Midland, Tx
I'm a little OCD myself. After every turn, I take out anything I have in the headstock and tailstock and air off the entire lathe. I then take my shop vac to the floor and surrounding area. When I'm doing pens, I actually air off the lathe before I start any finishing so there are no particles around to get on my finish. Lol
 

Woodchipper

Member
Joined
Mar 15, 2017
Messages
3,292
Location
Cleveland, TN
Sticking your finger into the headstock or tailstock will introduce oils and perspiration that could result in rust. I use an old cloth and/or a shotgun bore mop of appropriate size. The air compressor is first, though.
 

mark james

IAP Collection, Curator
Joined
Sep 6, 2012
Messages
10,292
Location
Medina, Ohio
Sticking your finger into the headstock or tailstock will introduce oils and perspiration that could result in rust. I use an old cloth and/or a shotgun bore mop of appropriate size. The air compressor is first, though.

I would never have thought to do that... 🤭 🤭 🤭
 
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